The present invention relates generally to power generation equipment such as fuel cells, and particularly to thermal management of fuel cells, for example solid oxide fuel cells.
A fuel cell is an energy conversion device that produces electricity, by electrochemically combining a fuel and an oxidant across an ionic conducting layer. A high temperature fuel cell bundle for example a solid oxide fuel cell bundle is typically constructed of an array of axially elongated tubular shaped connected fuel cells and associated fuel and air distribution equipment. Alternative constructions to the tubular fuel cells are planar fuel cells constructed from flat single members. The planar fuel cells can be of counter-flow, cross-flow and parallel flow varieties. The members of a typical planar fuel cell comprise tri-layer anode/electrolyte/cathode components that conduct current from cell to cell and provide channels for gas flow into a cubic structure or stack.
In a solid oxide fuel cell, the oxygen ion transport (O2−) across the electrolyte produces a flow of electrons in an external load. The waste heat generated in a solid oxide fuel cell at its operating temperature from about 600° C. to about 1300° C. is typically removed via an oxidant in order to maintain a desired temperature level of the fuel cell components such as the anode, cathode and electrolyte.
Fuel cells such as solid oxide fuel cells have demonstrated potential for high efficiency and low pollution in power generation, however, there are problems associated with thermal management particularly in the temperature regulation of fuel cell components. Thermal energy generated in a fuel cell from the reaction of a fuel and an oxidant needs to be removed or used internally in order to maintain the operating temperature. Cooling channels in planar fuel cell or cooling tubes in tubular fuel cells use oxidant, typically air, to aid in the transfer or removal of waste heat so as to maintain a stack temperature at or below prescribed limits and maintain a predetermined thermal gradient. Such channels or cooling tubes, as used in conventional fuel cell applications have low convective thermal transfer coefficient between the fluid flow channel and the oxidant. Accordingly there is a need in the art to address improved cooling requirements of fuel cell with improved heat transfer characteristics.